Thursday, December 15, 2016

The sole mention of the arcuballista occurs in the work of
Vegetius (Epitoma rei militaris)[1].
In book II.15, when describing how the ancient legion was drawn up in
battle order, he refers to soldiers who shoot bolts with manuballistae and arcuballistae,
terms which are typically translated as catapults and crossbows respectively.

In
etymological terms, Latin ballista is
taken from the Greek βαλλίστρα‎(ballístra), itself
derived fromβάλλω(bállō,“I throw”). So, manuballista (the Latin variant of the Gr. cheiroballistra) has the sense of “hand projector”. Most scholars[2][3][4][5] seem to agree
that this weapon was a torsion-powered bolt-shooter, but debate on its configuration
is effectively divided into two camps: those who accept the translation
literally and believe the manuballista
was hand-held and, conversely, those who see it as a continuation and
technological development of earlier stand-mounted catapults as seen, for
example, on Trajan’s Column.

As for the arcuballista, its name suggests it incorporated an arcus (Lat. “arch”), but whether this
refers to the bow of a non-torsion weapon or to the arched-strut (Lat. arcus ferreus) design of torsion weapons
from the 2nd century AD onwards cannot be unequivocally stated.

However,
in Book IV of Epitoma Rei Militaris (op.
cit. IV.22), while discussing siege
and naval warfare, Vegetius continues to make a clear distinction between the
weapons “they used to call ‘scorpions’ what are now called manuballistae” and those such as fustibali (“staff-slings”), arcuballistae
(crossbows) and slings. Unfortunately
Vegetius does not describe the latter any further assuming that his
contemporary readers would be familiar with their form and function. Weapons such as slings and staff-slings are
clearly hand-held weapons however and, by implication, so must arcuballistae. Moreover, by repeatedly referring to manuballistae and arcuballistae separately Vegetius, and other authors such as
Arrian, is clear that the latter are different from torsion powered
bolt-shooters and stone-throwers. So, if
arcuballistae are not
torsion-powered, then it seems logical that they were very similar to medieval
crossbows using flexion bows.

Thus we turn to the crossbows depicted on the
Gallo-Roman reliefs (shown below) from Salignac (left) and Saint Marcel (right)[6]. These are obviously not gastraphetes (belly-bows) as they lack the distinctive
crescent-shaped stomach rests characteristic of such weapons. Nor is there any sign of winching mechanism
for spanning the bows. Are these then
the elusive arcuballistae?

From a photograph
of the Salignac relief in
his article[7], Baatz suggests a plausible reconstruction of an arcuballista:

It is unclear whether the
reliefs depict self-bows or composites; both were known and used by the
Romans. A reconstruction of a arcuballista could, quite reasonably,
use either. It is unlikely that a steel
prod was used as in later medieval crossbows, however.

No known contemporary
spanning devices have been discovered, and none are shown on the surviving
French reliefs. To span an arcuballista, a sketch in Baatz shows
the arcuballistarius placing a foot
on the belly of the bow, either side of the stock, and drawing the bowstring by
hand. So, the draw weight of the arcuballista cannot be so great that the
bow cannot be spanned by hand.

A visual assessment of the Saint Marcel relief
suggests the stock was between 60 cm and 70 cm in length using the forearm of
the arcuballistarius as a cubit
measure; the average cubit being 47 cm (»0.5 m).Likewise,
using the same method of measurement, a bow length of c. 130 cm (tip to tip),
as Baatz' suggests, is plausible.

Using the length of the depicted quiver on the
relief from Saint Marcel, Baatz makes the assumption that missiles were of
similar length to arrows shot from standard bows. Furthermore, with the nut placed at the end
of the stock, Baatz also assumes that the draw length was longer than that of
later crossbows, and thus longer arrows could be used rather than shorter
bolts.

From the Saint Marcel relief there does appear to be a
revolving nut. Finds of something
similar have been discovered in Britain and dated to the 5th or 6th
century AD. These, quite naturally, have
been attributed to a form of late Roman crossbow.Releasing the nut may well
have been effected with a trigger bar beneath the stock in similar fashion to
medieval weapons. Drawing back of the
round handle at the rear of the stock might equally have been involved in
releasing the nut. Pushing the handle
forward may have engaged a straight trigger bar in a notch integral to the
revolving nut. Precisely how the
mechanism operated, however, remains a matter of conjecture.References:

About Me

We are historical interpreters and presenters who teach in schools and colleges, deliver living history demonstrations at events across Great Britain, and carry out reconstructive or experimental archaeology to better understand the lives of our forebears.